[TenTec] On Noisy Transmitters

[Jim Brown]

On 7/6/2014 7:07 AM, Rick - DJ0IP / NJ0IP wrote:
> Cheap is cheap in more ways than most people realize.

YES! Wayne, N6KR, talked about phase noise and what he did to minimize 
it. In a different email (can't find it right now), he talked about what 
he did to minimize clicks.

Clicks are generated by rise times that are too fast combined with 
intermod distortion. Think of CW as an amplitude modulated carrier, 
where the modulation is a square wave. A square wave consists of an 
infinite number of harmonics. The faster the rise (and fall) time, the 
more harmonics, and the higher order harmonics will be stronger. Those 
harmonics, then, interact with IM distortion to produce sidebands. Those 
sidebands are the clicks. That analysis is mine.

What Wayne said (I'm paraphrasing) is that he developed  optimal shaping 
for the square wave that minimizes those harmonics while still providing 
nice, distinct keying at high speeds. If I remember correctly, he called 
it "sigmoidal," after the mathematical name for the function that he 
used. He noted that it takes a lot of DSP cycles to do that, as well as 
a lot of programming, and that when you're doing that, there are other 
things you cannot do because you've dedicated the DSP to that function.

The point is that Wayne and Eric made the design and marketing decision 
that having a very clean TX signal was the highest priority. I don't 
know much about the current Ten Tec rigs, but I do know that when Al 
Kahn was around, that was also a very high priority for Ten Tec.

73, Jim K9YC